1. Technical Field
This invention relates generally to sleeves for protecting elongate members and more particularly to EMI/RFI/ESD shielding yarns and sleeves constructed therefrom.
2. Related Art
It is known that electromagnetic interference (EMI), radio frequency interference (RFI), and electrostatic discharge (ESD) can pose a potential problem to the proper functioning of electronic components caused by interference due to inductive coupling between nearby electrical conductors and propagating electromagnetic waves. Electronic systems generate electromagnetic energy due to the flow of current within a circuit. This electromagnetic energy can adversely affect the performance of surrounding electronic components, whether they are in direct communication within the circuit, or located nearby. For example, electrical currents in conductors associated with an electrical power system in an automobile may induce spurious signals in various electronic components, such as an electronic module. Such interference could downgrade the performance of the electronic module or other components in the vehicle, thereby causing the vehicle to act other than as desired. Similarly, inductive coupling between electrical wiring in relatively close relation to lines carrying data in a computer network or other communication system may have a corrupting effect on the data being transmitted over the network.
The adverse effects of EMI, RFI and ESD can be effectively eliminated by proper shielding and grounding of EMI, RFI and ESD sensitive components. For example, wires carrying control signals which may be subjected to unwanted interference from internally or externally generated EMI, RFI and ESD may be shielded by using a protective sleeve. Protective sleeves can be generally flat or cylindrical, wherein the sleeves are formed from electrically conductive and nonconductive constituents, with the conductive constituents typically being grounded via a drain wire interlaced with the yarns during manufacture of the sleeve. Known conductive constituents take the form of nonconductive fibers or filaments, such as nylon, coated with a conductive metal, such as silver. Other known conductive constituents are fabricated by impregnating a nonconductive resin with micro fibers of metal, such as stainless steel, copper or silver, or with micron size conductive powders of carbon, graphite, nickel, copper or silver, such that the micro fibers and/or powders are bonded in conductive communication.
While such RFI, EMI, and ESD sleeving made with coated conductive yarns is generally effective at eliminating electrical interference, the sleeving can be relatively expensive in manufacture, particularly when expensive coatings, such as silver, are used. In addition, conductive coatings can be worn off, leading to inefficiencies in conductive connections between the conductive constituents, thereby impacting the ability of the sleeving to provide optimal RFI, EMI, and/or ESD protection. Accordingly, RFI, EMI, ESD shielding which is more economical in manufacture, and more efficient in use, and more reliable against wear and having an increased useful life, is desired.
A sleeve manufactured from fabric according to the present invention overcomes or greatly minimizes at least those limitations of the prior art described above, thereby allowing components having potential adversarial effects on one another to function properly, even when near one another.